Inhibition of tumor necrosis factor-alpha-induced RANTES secretion by alkaline protease in A549 cells

• Published in: American journal of respiratory cell and molecular biology Vol. 33; no. 5; pp. 483 - 489
• Main Authors: Krunkosky, Thomas M, Maruo, Keishi, Potempa, Jan, Jarrett, Carla L, Travis, James
• Format: Journal Article
• Language: English
• Published: United States American Thoracic Society 01.11.2005
• Subjects: Antibodies, Blocking - pharmacology; Bacterial Proteins - pharmacology; Cell Membrane - chemistry; Cells, Cultured; Chemokine CCL5 - genetics; Chemokine CCL5 - metabolism; Endopeptidases - pharmacology; Epithelial Cells - drug effects; Epithelial Cells - metabolism; Gene Expression - drug effects; Humans; Lung - cytology; Pseudomonas aeruginosa - enzymology; Receptors, Tumor Necrosis Factor, Type I - analysis; Receptors, Tumor Necrosis Factor, Type I - antagonists & inhibitors; Receptors, Tumor Necrosis Factor, Type I - metabolism; RNA, Messenger - metabolism; Tumor Necrosis Factor-alpha - antagonists & inhibitors; Tumor Necrosis Factor-alpha - pharmacology
• ISSN: 1044-1549; 1535-4989
• DOI: 10.1165/rcmb.2005-0069OC

Pseudomonas aeruginosa is a gram-negative bacterium that is an opportunistic pathogen in patients with cystic fibrosis and in immunocompromised hosts. This bacterium produces a variety of proteolytic enzymes, including alkaline protease (AP), which has multiple biological effects. This study investigated the effects of AP on the A549 pulmonary epithelial cell line. Results demonstrate that AP inhibited tumor necrosis factor (TNF)-alpha-induced RANTES gene expression and secretion in a concentration-dependent manner. The TNF-alpha-induced RANTES gene expression and secretion was attenuated with a neutralizing monoclonal antibody directed against the TNF receptor type 1 (TNFR1). Conversely, a neutralizing monoclonal antibody directed against TNF receptor type II had no effect, suggesting that these events were regulated through the TNFR1 receptor. In addition, we observed that soluble TNF receptor type 1 (sTNFR1) levels were significantly increased in culture supernatants of AP-treated cells in a concentration-dependent manner. Finally, membrane-associated TNFR1 was decreased after AP exposures. In these studies, the enzymatically inactive form of AP had no effect on TNF-alpha-induced RANTES secretion, shedding of sTNFR1, or membrane-associated TNFR1. These results demonstrate that AP stimulates shedding of cell-surface TNFR1, resulting in an increase in sTNFR1. Consequently, these events decrease the cells' ability to stimulate RANTES gene expression and secretion through TNFR1.